Linux FHS(Filesystem Hierarchy Standard)

/ (root directory):

The top-level directory in the file system hierarchy.

Only root user has write privilege under this directory.

/bin:

Essential command binaries that are required for the system to boot and run.

Commands used by all the users of the system are located here.

For example: ps, ls, ping, grep, cp.

/boot:

Contains files needed for the boot process, such as the kernel, initramfs, and bootloader configuration.

/dev:

Device files, representing hardware devices connected to the system.

/etc:

Configuration files and directories containing system-wide configuration files.

This also contains startup and shutdown shell scripts used to start/stop individual programs.

For example: /etc/resolv.conf, /etc/sysconfig/network-scripts/ifcfg-eth0

/home:

Home directories for users.

/lib and /lib64:

Essential shared libraries and kernel modules.

/media:

Mount points for removable media (e.g., USB drives, optical discs).

/mnt:

Mount points for temporarily mounted filesystems.

/opt:

Optional application software packages.

/proc:

A virtual filesystem that provides information about processes and system configuration.

/root:

Home directory for the root user.

/run:

A tmpfs (temporary file system) mounted at boot to store runtime information.

/sbin:

System binaries, which are essential for system administration but not for regular users.

/srv:

Data for services provided by the system.

/sys:

A virtual filesystem that exposes information about the kernel, devices, and other kernel-related information.

/tmp:

Temporary files are usually cleared on system reboot.

/usr:

Secondary hierarchy containing user and system binaries, libraries, documentation, etc.

/var:

Variable files — files that may change in size or content during the course of normal system operation (e.g., logs, spool files).